The plan calls for AC Transit to run its existing late-night lines that run from San Francisco to Richmond and Fremont more frequently and add a line to the Pittsburg-Bay Point BART station. The routes would also be lengthened in San Francisco to 24th and Mission streets.

Buses would run every 20 minutes between 12:30 and 2:30 a.m., about the frequency of BART trains during non-commute hours.

Bus riders will pay a $4.20 fare for a trip across the Bay and the regular AC Transit fare of $2.10 for local trips.

AC Transit officials said the pilot program augments their regular "owl service" that began in 2005 to provide important transbay service for hundreds of night-shift workers and others from 12 a.m. to 5 a.m., when BART trains have stopped for the night.

AC Transit Board President Greg Harper said in a statement, "This is the first implementation of several joint projects AC Transit is planning with BART."

Harper said, "We are happy to do all that we can to support inter-agency transit projects that move us toward seamless transit service for the Bay Area."

BART Director Robert Raburn said, "These extra buses will provide more frequent and expanded service to those who rely on transit when BART isn't in service."

Raburn said, "This pilot program is part of a larger effort to seek ways to offer the public more options during the overnight hours."

BART officials said they're not able to operate trains during overnight hours because they lack extra tracks to run trains on while they perform essential overnight track maintenance to keep the rails safe and reliable.

BART developed the late night bus plan after three years of study. BART has anticipated the program will cost $838,000 and has secured $496,000 in grants and set aside $200,000 in operating funds. It anticipates recovering $100,000 in fare revenue from the buses.